The present invention relates to a method of cutting a workpiece by using a cutting blade having an annular cutting edge.
In the production of semiconductor devices, for example, a surface of a nearly disk-like semiconductor wafer is sectioned into a plurality of rectangular sections by the cutting lines called streets that are arranged in a form of a lattice pattern, and a predetermined circuit pattern is formed on each of these rectangular sections. The plural rectangular sections on which the circuit pattern is formed are cut into individual pieces to form so-called semiconductor chips. The cutting of the semiconductor wafer is usually carried out by using a precision cutting machine called dicing machine. The dicing machine is equipped with a cutting blade having an annular cutting edge. The workpiece is moved relatively to the cutting blade in a direction at right angles to the rotary shaft of the cutting blade to execute the cutting.
On the semiconductor wafer is formed laminated circuit wiring. The wiring is generally formed of aluminum. In recent years, however, study has been forwarded to put a copper foil into a practical use. That is, copper has an electrical resistivity as small as 1.7 xcexcxcexa9-cm which is about one-half the electrical resistivity of aluminum, and consequently, makes it possible to realize a wiring of a width of 0.15 xcexcm to cope with a high degree of integration as well as to increase the speed of critical path by at least 30%. Besides, wiring of copper can be produced at a lower cost compared with that of aluminum and hence, copper is drawing attention as a wiring material to substitute for aluminum.
When the semiconductor wafer on which the copper foil is laminated is cut by using the dicing machine, plural whisker-like burrs of lengths of about 20 to 50 xcexcm are formed on both sides of a groove that has been formed by cutting. These burrs could cause troubles such as a short-circuit among the laminated layers and among the bondings or injury. Besides, burrs that have come off could cause damage to the circuits. It is considered that the burrs are formed since copper is soft and viscous and is likely to be easily deformed.
It is an object of the present invention to provide a cutting method which does not produce burrs at the time of cutting a workpiece on which is laminated a metal foil which is soft, viscous and likely to be easily deformed, such as copper, gold or silver, and particularly at the time of cutting a semiconductor wafer on which the metal foil is laminated as a wiring of an integrated circuit.
In order to accomplish the above-mentioned object according to the present invention, there is provided a cutting method of cutting a workpiece by moving the workpiece relatively to a cutting blade that has an annular cutting edge and rotates in a predetermined direction, the workpiece being moved in a direction at right angles to the rotary shaft of the cutting blade, wherein the cutting method comprises:
a cutting step of cutting the workpiece by moving the workpiece in a forward direction in respect to the rotational direction of the cutting blade at a position where the blade and the workpiece face each other; and
a burr-trimming step for tracing the groove cut by the cutting step by moving the workpiece in a direction against the rotational direction of the cutting blade at a position where the blade and the workpiece face each other.
The invention further provides a cutting method by successively executing the cutting step and the burrtrimming step by reciprocatingly moving the workpiece relative to the cutting blade that rotates in the predetermined direction, feeding the cutting blade for indexing a cutting line that is to be cut next, and executing the cutting step and the burr-trimming step by reciprocatingly moving the workpiece.
It is desirable that a relative moving speed between the cutting blade and the workpiece in the burr-trimming step is set to be greater than a relative moving speed between the cutting blade and the workpiece in the cutting step.